Heat treating apparatus



NOV 9, 1937. L. B. RossEAu HEAT TREAT ING APPARATUS Filed Nov. 24, 1936 Inventor: L eOr B-Rosseau,

His Atorney.

Patented Nov. 9, 1937 UNITED STATES PATENT OFFICE HEAT TREATING APPARATUS Application November 24, 1936, Serial No. 112,529

4 Claims.

My invention relates to apparatus for the heat treatment of articles by immersion in a liquid or molten bath. The practice for such heat treatment as followed in the past has been to lower 5 the article into a furnace containing the molten bath so as to immerse it in the bath to the desired depth, to maintain it immersed for the desired time and nally to withdraw it from the furnace all under the manual control of the operator. In certain cases it is desirable for the proper heat treatment of the article that the immersion be carried on in successive steps of various depths, the article being held for various time intervals between the successive steps.

Difficulty has been experienced in the past, particularly in those cases in which an exact immersion depth and time schedule must be adhered to where dependence for the carrying out of such a schedule has rested entirely upon the operator. The immersion depth in particular has not been sufficiently closely regulated since the exact depth to which the article was lowered into the furnace has been determined heretofore solely by the observation of the operator. 'I'his has been made the more diflicult because of the fact that the liquid level of the bath does not remain the same but varies during the day since more or less of liquid clings to each article.

It is the object of my invention, therefore, to 30 provide improved apparatus for such heat treatment whereby the above-mentioned diillculties are avoided.

My invention will be better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

In the single figure of the drawing which is a combined side view and circuit diagram of a preferred embodiment of my invention, I represents the furnace and 2 the crucible therein containing the molten lead. 'I'he furnace is of a well known construction having a fire-clay tile inner portion I upon which the electric heating units l are supported and having a thick layer of heat insulating material surrounding the tile, the entire assembly being enclosed in the sheet steel casing 6. 'I'he upper end of the crucible has a flange by which it is supported by the outer casing of the furnace. Since the crucible in this case is me- 50 tallic, being preferably formed of an alloy, the lead bath is in electrical connection with the outer casing of the furnace.

At 1 I have represented an article such as a steel forging which is to be heat treated in the furnace. The article 1 is shown supported by means of the chuck I from the rack 9 which it will be understood is mounted in suitable guides, not shown, for vertical movement. For lowering the article 1 into the lead bath and subsequently raising it therefrom I have shown the shunt wound electric motor ill which connects with the rack 9 through the worm gearing ii and the spur gear i2. The `armature circuit of motor III is shown connected through the solenoid actuated reversing switch i4 and the manual switch i5 with the source of direct current supply I6. With the switch I4 in the position shown on the drawing a closing of the switch l5 will cause the motor l0 to operate in a direction to lower the article 1 into the furnace.

In accordance with my invention as soon as the article 1 makes contact with the molten lead in the furnace the manual control of the motor is disconnected and an automatic control thereafter is substituted. This substitution of con- 2 trol is effected through the relay il having the rod i9 which when the relay is energized engages the switch I5 to move it to open circuit pomtion. One end of the winding of relay il connects with the positive side of the source of supply it and the other end of the winding connects by means of the flexible connection 20 with the rack 9; hence it is electrically connected with the article 1. The negative or grounded side of the source of supply connects directly with the outer casing 6 of the furnace which also is suitably grounded through its supporting structure, the rack and the associated parts of the structure being insulated from ground. If desired, the rack may be grounded and the furnace insulated in which case the connections to the source IS would be reversed; however, such an arrangement is subject to the production of static because of leakage from the heating units employed, the static shocks sometimes interfering with the eiilciency of operators when engaged in adding metal to the crucible. I prefer, therefore, to connect the apparatus in the manner shown. When, therefore, the motor is operated by the manual closure of switch l5 the article is lowered until it engages the surface of the molten lead at whatever height it may be at which time the circuit of relay Il is closed rendering the manual control inoperative and substituting therefor an automatic control for the further immersion of the article.

Various forms of apparatus may be employed to control the depth at which the article is immersed in the leadl the number of steps by which it is immersed. and the length of time which it is maintained immersed at each step. I shall now describe a simple form of such control apparatus lll by which the article is automatically immersed in the liquid in two steps and maintained stationary at those steps for predetermined lengths of time after which the article is withdrawn from the furnace.

The energization of relay i8 not only opens the switch l but closes a shunt circuit around that switch at the contacts 2l whereby the motor it continues to operate to lower the article l into the lead. Relay is, also, by its energizaton closes at its contacts 22 a circuit which includes the Winding of the time delay relay 23, which relay is provided with the dash pot 2l having means for variably controlling the upward movement ci' the movable contacts when the relay is energized. This relay functions in he manner of a limit switch whereby after the motor it has operated to lower the article l for a predetermined time it opens the motor circuit at the contacts 25 and simultaneously closes at the contacts 26 the circuit or the time delay relay 2l. 'l'his relay is provided with a controlled dash pot like that of relay it and serves to determine the length of time at which the article remains immersed in the first step, the depth of immersion lacing represented, for example, by the dotted lines 2t. At the expiration o f: that time the relay' il recloscs the'motor circuit at the contacts lil and simultaneously at the contacts it@ lcloses the circuit of the time delay relay 3l. This relay islikewise provided with a controlled dash not and functions as a limit switch to ccntrol the distance at which the article is again lowered in. the lead bath. At the expiration of the time for which this relay 'is set it opens the motor circuit again at the contacts 32 and simultaneously closes at the contacts the circuit ci the time delay relay til which like relay is provided with, controlled dash pot. 'lhis relay like .relay ill controls the length of time the article is immersed in thel second step represented by the dotted lines At the expiration ci? the time for which relay 3&1 is set it closes the circuit oi the time delay relay which is also provided with a controlled dash pot tout the dash pot in this case'operates in the reverse manner, that is, the relay operates without delay upon'heing energized but opens a circuit controlled thereby under the control of the dash pot. The operation of the relay 3u closes the circuit oi the solenoid 3l which moves the reversing switch to the position opposite to that shown on the drawing whereby the direction of rotation of the motor is reversed and the article l is immediately withdrawn from the furnace. As soon as the article breaks connection with the bath the relay I8 becomes deenergized and accordingly each of the succeeding relays in turn becomes deenergized. After the brief time for which relay 3S is set, which time is sufcient for the motor to lift the article clear of the top of the furnace, the relay 3G functions to open the circuit of the solenoid 3l whence the reversing switch drops to the position shown. Since the motor circuit is open at the manual switch I5, the motor comes to rest.

The article l may now be disconnected from the rack 9 and another article substituted therefor, the control apparatus being in position for repetition of the operation just described.

From the above it will be seen that the depth of immersion of an article and the length of time it is held immersed is entirely independent 0f the operator and independent of the height ot the liquid in the Crucible. While the lowering ci the article is initiated manually, as soon as it touches the surface of the bath the manual control is taken over by the automatic means for the control of the depth and time of actual immersion.

What I claim as new and desire to secure by Letters Patent of the United States, is:

`l. In combination, a molten bath, means for lowering an article into engagement with said bath to be heat treated therein, a circuit arranged to be closed by the contact oi said ar-Av ticle with said bath and means responsive to the closing of said circuit for controlling the immersion of lthe article into the bath.

2. ln combination, a molten bath, manually controlled means for lowering an article into engagement with said bath to he heat treated therein, a circuit arranged to be closed by the contact of said article 'with said bath and mea-ns responsive to the closing of said circuit for controlling the lowering of the article to a predetermined distance into said bath.

3. ln combination, a molten hath, means for lowering an article into engagement with said bath to be heat treated therein, a circuit arranged to be closed by the contact of said article with said bath, means rendered operative by the closing of said circuit for controlling said lowering means after said article has engaged the bath and time delay means for controllingthe time of immersion of said article in said bath.

l. in combination, a Crucible containing molten lead, motor controlled apparatus for lowering an article into said lead, manual means for controlling said motor, a circuit connected with said crucble and with said article arranged to be closed by the contact of the article with the lead and means responsive to the closing of said circuit for assuming control of said motor.

LEON B. ROSSEAU. 

